The invention relates generally to the field of image processing having image understanding that automatically classifies pictures by events and the like and, more particularly, to such automatic classification of pictures by block-based analysis which selectively compares blocks of the images with each other.
Pictorial images are often classified by the particular event, subject or the like for convenience of retrieving, reviewing, and albuming of the images. Typically, this has been achieved by manually segmenting the images, or by the below-described automated method. The automated method includes grouping by color, shape or texture of the images for partitioning the images into groups of similar image characteristics.
Although the presently known and utilized methods for partitioning images are satisfactory, there are drawbacks. The manual classification is obviously time consuming, and the automated process, although theoretically classifying the images into events, is susceptible to miss-classification due to the inherent inaccuracies involved with classification by color, shape or texture.
Consequently, a need exists for overcoming the above-described drawbacks.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, the invention resides in a method for comparing image content of first and second images, the method comprising the steps of: (a) extracting a portion of both the first and second images both of which portions are determined to include a main subject area of each image; (b) dividing the main subject area of the images into a plurality of blocks; (c) computing a color histogram for one block in each image; (d) computing a histogram intersection value between the block of the first image and the block of the second image; and (e) determining a first threshold value for the computed histogram intersection value that determines similarity between the block in the first image and the block in the second image.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.
The present invention has the advantage of improved classification of images by utilizing block-based comparison that checks for similarity between two images, and for near-duplicate images.